Bending machine



Nov. 29, 1966 H. VAN HARTEN BENDING MACHINE Filed pril 1, 1964 2 Sheets-Sheet 1 INVENTOR HERBERT VAN HARTEN Nov. 29, 1966 H. VAN HARTEN 3,

BENDING MACHINE Filed April 1, 1964 2 Sheets-Sheet 2 IN VENT O HERBERT VAN HARTEN 7f Mae Z J. 5 f mr hi5 ATTORNEY United States Patent 1 Claim. 61. 72-150) The present invention relates to bending machines in general, and more particularly to a pipe bending machine. Still more particularly, the invention relates to improvements in rotary pipe bending machines wherein lengths of pipe are bent about rotary forms while the walls of pipe sections which are located just ahead of the point where bending begins receive a suitable mandrel which prevents collapsing of the pipe walls. In such machines, the pipe may but need not be held by pressure dies.

It is an important object of the invention to provide a novel form for use in rotary pipe bending machines.

Another object of the invention is to provide a novel shifting arrangement which controls movements of the mandrel in such bending machines and to construct the shifting arrangement in such a way that axial movements of the mandrel are properly synchronized with angular movements of the novel form.

A further object of the invention is to provide a shifting arrangement of the just outlined characteristics which allows the mandrel and the pipe to move in one or more directions other than axially so as to make sure that the pipe will follow the curvature of the form with utmost accuracy and that tubular stock of different gauge may be bent in the same machine.

A concomitant object of the invention is to provide a rotary bending machine for tubular stock which is capable of producing comparatively simple or more complicated bends ranging from bends which follow the periphery of a circle to bends whose curvature changes gradually or even suddenly and wherein the minimum radius of curvature may be but a small fraction of the maximum radius.

With the above objects in view, a very important feature of the invention resides in the provision of a bending machine, particularly a rotary bending machine for pipes and similar tubular workpieces, wherein the rotary form comprises a peripheral bending surface arranged to engage and to bend a workpiece in response to rotation of the form, and wherein this bending surface includes sections having different radii of curvature so that the bent portion of the pipe need not follow the periphery of a circle. The centers of curvature of all surface sections may but need not be located on the axis about which the form rotates, and the transition between such sections may but need not be gradual.

Another feature of the invention resides in the provision of a specially mounted mandrel which is movable axially to insure that the position of its leading end portion is always in proper relation to the angular position of the form.

A further feature of the invention resides in the provision of a mandrel which is movable sideways, i.e., substantially at right angles to its axis, to make sure that its tip'can remain sufliciently close to the bending surface of the form.

Still another feature of the invention resides in the provision of an adjustable pressure die which insures that the form will bend only that portion of the pipe which is in actual engagement with the bending surface.

, The novel features which are considered as characteristic of the invention are set forth in particular in the appended claim. The improved bending machine itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawings, in which:

FIG. 1 is a somewhat schematic side elevational view of an automatic pressure-die type rotary pipe bending machine which embodies the invention;

FIG. 2 is a somewhat schematic top plan view of the bending machine; and

FIG. 3 is a greatly enlarged view of a portion of the structure shown in FIG. 2.

Referring to the drawings, the bending machine comprises a fixed base 10 having a horizontal arm 11 which supports a specially configurated form 12. The form is rotatable about the axis of a vertical shaft 13 and is driven by an electric motor 14 provided at the underside of the arm 11. A cable 35 is fixed to a pulley 36 on the shaft 13 and to a counterweight 37 to automatically return the form 12 to-the angular position of FIG. 2 or 3 when the machine completes a bending operation.

The form 12 cooperates with an elongated bar-shaped clamping die 15, with a block-shaped or rail-shaped pressure die 16, and with a mandrel 17. The clamping die 15 is reciprocable radially of the shaft 13 and is guided in ways 38 provided on a horizontal carrier 39 which is rotatable with the form 12. The slide 40 which serves to move the clamping die 15 along the ways 38 is of known design and its exact construction forms no part of this invention.

The pressure die 16 is pivotable about a vertical pin 16a provided at one end of an L-shaped supporting bracket 41 mounted on a second carrier 42 having horizontal ways 43 so that the die 16 may move in directions substantially at right angles to the axis of the mandrel 17. The means for moving the bracket 41 along the ways 43 comprises a hydraulically or pneumatically operated slide 24 which may be replaced by a spring or by a package of springs.

If desired, the block-shaped die 16 may be replaced by a roller having a peripheral groove similar to the groove in the peripheral bending surface of the form 12.

The workpiece 18 is a length of pipe which is slipped onto the leading end portion of the mandrel 17 in a direction from the left, as viewed in FIG. 2, so that its trailing end portion enters the space between the jaws of a chuck 19. The chuck 19 is mounted on a tube 44 which surrounds the mandrel 17 and which is carried by a slide 20. This slide is mounted on two horizontal tie rods 21 extending between two fixed platens 45, 46 provided on the base 10 and being substantially parallel with the mandrel 17. The pipe 18 is inserted when the dies 15 and 16 are moved away from the form 12, and the slide 20 is then shifted to a starting positionin which the leading end portion of the pipe extends slightly beyond the clamping die 15. The slide 20 can be reciprocated by a hydraulic, pneumatic or electric motor and carries suitable control elements, here shown as limit switches 23, which cooperate with adjustable trips 22 provided on a third tie rod 47. The switches 23 may be connected in circuit with and then control the motor 14 so that this motor may be started, arrested or its speed adjusted in response to movement of the slide 20 toward the platen 45.

When the pipe 18 has been moved to the position of FIGS. 2 and 3, the die 15 is caused to move toward the form 12 and to clamp the pipe to make sure that the pipe will move endwise in response to rotation of the form about the axis of the shaft 13 whereby the slide 20 follows such movement because it is connected with the pipe via chuck 19 and tube 44. The carrier 39 also rotates about the axis of the shaft 13 to insure that the a pipe 18 is bent around the peripheral bending surface of the form 12 because the pipe remains clamped between the form and the die 15.

Before the pipe 18 begins to move in a direction to the left, as viewed in FIG. 2, the pressure die 16 is caused to engage the pipe in a zone just behind the clamping die 15. The die 16 insures that the bending operation is carried out with requisite precision by preventing bending of that section of the pipe which is not in contact with the bending surface of the form 12. In other words, the die 16 actually assists the mandrel 17. When the pipe 18 is bent, the form 12 is rotated in a counterclockwise direction, see the arrow 25 in FIG. 3.

In accordance with a very important feature of the present invention, the peripheral bending surface of the form 12 does not follow the periphery of a circle. Thus, the radius of curvature R of the surface section 12a is substantially greater than the radius of curvature r in a zone between the surface sections 12b and 120 which means that, as the form 12 rotates, the freshly bent sections of the pipe 18 will move closer to the shaft 13. In the embodiment of FIGS. 1 to 3, the radius r approximates about one-half of the radius R. Thus, the bent section of the pipe 18 will not resemble one-half of a circle but will resemble a more complicated curve.

Of course, and as the bending operation progresses, the pipe 18 will have to move sideways in a direction (see the arrow 26 in FIG. 3) which is substantially perpendicular to the axis of the mandrel 17. This is due to the fact that the surface section 1211 or 120 on the periphery of the form 12 is much nearer to the shaft 13 than the surface section 12a.

The mandrel 17 not only follows such sidewise movement of the pipe 18 but, in accordance with another important feature of my invention, also moves axially with reference to the pipe to make sure that its axial position with respect to the pipe is in proper relation to the radius of curvature of that section of the bending surface of the form 12 which is located opposite the pressure die 16, i.e., which is in the process of deforming a fresh section of the pipe 18.

In order to carry out such axial movement with reference to the pipe 18, the mandrel 17 is shiftable with respect to the slide 20. As shown in FIGS. 2 and 3, the mandrel is mounted in a head 27 which is carried by the slide 20 and which is biased by one or more helical expansion springs 27a tending to shift the mandrel in a direction away from the slide 20. The bias of the spring or springs 27a is opposed by an adjustable arresting device 28 which may include a fluid-operated cylinder connected with flexible fluid-admitting and evacuating conduits 28a, 28b and a piston rod fixed to the slide 20. The device 28 will arrest the mandrel 17 in a selected optimum position, for example, in a position which is best suited for introduction of a fresh length of pipe 18 when the dies 15, 16 are spaced from the form 12. This is of particular importance when the pipe 18 is delivered by an automatic feed mechanism, i.e., when it is necessary to keep the mandrel in a predetermined starting position to make sure that the mandrel will be properly received in the pipe.

The mandrel 17 or its supporting rod extends rearwardly and beyond the head 27 and its trailing end portion may be pivotable about a fixed vertical axis, or its trailing end portion may move sideways in and counter to the direction indicated by arrow 26. FIG. 2 shows that the base carries a support here shown as a rail 29 defining elongated horizontal ways for a slide 30 which supports the trailing end portion of the mandrel 17 so that the latter is movable sideways in directions at right angles to its axis. The position of the slide 30 may be controlled by a pneumatic or hydraulic cylinder (not shown) corresponding to the cylinder of the arresting device 28 and/or by a spring corresponding to the spring means 27a.

The slide 24 insures that the pressure die 16 follows the pipe 18 in the direction indicated by arrow 26.

The means for shifting the mandrel 17 axially with reference to the pipe 18 includes a first hydraulic or pneumatic cylinder 31 which is mounted on the slide 30 and is fixed to the trailing end portion of the mandrel, and a second hydraulic or pneumatic cylinder 32, both shown in FIGS. 1 and 2. The cylinders 31, 32 are respectively connected with flexible conduits 31a, 31b and 32a, 32b and the system of valves 48 which control admission and evacuation of fluid through these conduits is preferably controlled by one or more cams or trips which rotate with the form 12 to make sure that all axial movements of the mandrel 1'7 with reference to the pipe 18 are fully synchronized with angular movements of the form. The operative connection between the form 12 and the valves 48 for the cylinders 31, 32 may be constructed in a number of ways. This connection is indicated in FIG. 1 by a heavy phantom line 49. If desired, the valves 48 may be controlled by suitable time lag relays, not shown. It is also possible to provide for continuous automatic changes in the axial position of the mandrel 17 with reference to the pipe 18 by driving the mandrel 17 axially with the help of a suitable auxiliary motor (not shown) whose speed is controlled in correspondence with momentary angular position of the form 12. Such auxiliary motor also serves to return the mandrel 17 to a starting position as soon as the machine completes a bending operation. If desired, the auxiliary motor may be replaced by throttle valves mounted in conduits 31a, 31b, 32a, 32b and serving to insure that the cylinders 31, 32 will move the mandrel 17 gradually and at a rate corresponding exactly to changes in the angular position of the form 12. Such regulation of the speed of axial movement of the mandrel 17 will be necessary if the curvature of the form 12 changes gradually, i.e., if the zone of transition from the radius R to the radius r or vice versa extends along a substantial angle, as seen in the circumferential direction of the form.

In the embodiment of FIGS. 1 to 3, the cylinders 31 and 32 allow for coarse and precision adjustments in the axial position of the mandrel 17. The cylinder 31 takes care of coarse adjustments, and the cylinder 32 thereupon effects precision adjustment in exact accordance with the momentary angular position of the form 12. The piston of the cylinder 32 actually constitutes an element of the mandrel 17 and the trailing end of this composite mandrel is connected with the piston rod of the cylinder 31 which is reciprocable with and relative to the slide 30.

A further cylinder 33 serves as a means to open or close the chuck 19. This cylinder is connected with flexible conduits 33a, 33b leading to the slide 20 so that the chuck 19 may be opened or closed in a fully automatic way in dependency on the momentary position of the slide.

It will be noted that the trailing end portion of the mandrel 17 in the bending machine of FIGS. 1 to 3 is reciprocable sideways in a direction at right angles to the axis of the mandrel. This is due to the fact that the slide 311 is movable along the rail 29. However, and as mentioned hereinabove, it is also possible to modify the bending machine in such a way that the trailing end portion of the mandrel will be pivotable about a fixed vertical axis. This could be efiected by omitting the rail 29 and by providing a rigid connection between the base 10 and slide 30 or between the base 11 and cylinder 31. Such mounting of the mandrel 17 is advisable and possible when the difference between the maximum and minimum radii of curvature of the form 12 is rather small.

The numeral 34 indicates a device which serves to rotate and to fix the mandrel 17 in selected angular positions.

The quality of the bend in a pipe or in a similar tubular body will depend to a large extent on the axial position of the mandrel with reference to the pipe, and more particularly with reference to that section of the pipe which is about to be bent by the form 12 and dies 15, 16. It was found that bends of optimum quality will be obtained if the mandrel advances toward the leading end portion of the pipe whenever the radius of curvature of the bend diminishes. In other words, the mandrel 17 should move in a direction to the left, as viewed in FIG. 2, when the bending operation progresses because the radius of curvature of the surface section 1211 is less than that of the surface section 12a but exceeds the radius of curvature of the surface section 12C. On the other hand, andif the form 12 is replaced by a form which begins to bend a pipe along a surface section with a small radius of curvature and thereupon along one or more surface sections having greater radii of curvature, the mandrel 17 will have to move in a direction to the right, as viewed in FIG. 2 or downwardly, as viwed in FIG. 3. Of course, in the course of a normal bending operation, axial movements of the mandrel 17 will be rather small, normally in the range of a few centimeters or even a few millimeters. Nevertheless, such minimal axial adjustments of the mandrel will affect very strongly the quality of the ultimate product, both as regards its appearance and its strength characteristics. For example, if the pipe is bent about a surface section with a small radius of curvature and the leading end portion of the mandrel is too far behind the bending zone, the pipe will be flat at the bend. On the other hand, and if the pipe is bent along a surface section with a large radius of curvature and the leading end portion of the mandrel extends too far into the leading end portion of the pipe, the latter is likely to burst open along the outer side of the bend.

It will be noted that the direction of axial (endwise) movement of the mandrel will depend on the configuration of the form. If the form is configurated and mounted in a manner as shown in the drawings, the mandrel 17 will move in a direction to the left, as viewed in FIG. 2. If the form 12 is replaced by a form wherein a surface section with a small radius of curvature is first to engage the workpiece, the mandrel will move in the opposite direction. If the surface section with minimum or maximum radius of curvature is located between the ends of the peripheral bending surface of the form, the mandrel will move axially back and forth to account for changes in the radius of curvature.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can,

by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended vw'thin the meaning and range of equivalence of the following claim.

What is claimed as new and desired to be secured by Letters Patent is:

A rotary bending machine for pipes and similar tubular workpieces, comprising a base; a vertical shaft journalled in said base; a carrier mounted on said base and rotatable about the axis of said shaft; means for rotating said carrier; a form fixed to and rotatable with said carrier about the axis of said shaft, said form having a peripheral bending surface arranged to engage and to bend a workpiece in response to rotation of said carrier and said bending surface having sections with different radii of curvature; an elongated mandrel mounted on said base and having a leading end portion arranged to extend into the workpiece which is being bent up to a point close to said bending surface; first shifting means for moving said mandrel axially in synchronism with rotary movement of said form about the axis of said shaft so that the axial position of said mandrel is correlated to the angular position of said bending surface; second shifting means for moving said mandrel horizontally and sideways in a direction substantially at right angles to the axis of the mandrel; a clamping die provided on said carrier and arranged to clamp the leading end portion of the workpiece against said bending surface during rotation of said form; a chuck surrounding a portion of said mandrel and arranged to clamp the trailing end portion of the workpiece during bending; and a slide mounted on said base for movement in the axial direction of said mandrel and supportingly connected with said chuck so that the chuck and the workpiece may move axially of the mandrel when the form rotates about the axis of said shaft.

References Cited by the Examiner UNITED STATES PATENTS 1,714,083 5/1929 Frand 72-153 1,982,164 11/1934 Hoener 72-153 CHARLES W. LANHAM, Primary Examiner.

R. D. GREFE, Assistant Examiner. 

